Mobile Trojan launches Skulls attack

A new variant of the Skulls Trojan horse that affects Symbian-based cell phones has been discovered.

F-Secure has reported that Skulls.D kills off all system applications, as did previous variants. But rather than turning individual application icons into skulls, as the first version of the malicious software did, Skulls.D tells people their cell phones have been infected by displaying a full-screen flashing skull, the security software maker said on Monday.

The new Skulls variant pretends to be Macromedia Flash player and affects Symbian Series 60 devices. People whose handsets have been infected cannot run programs, take pictures or send text messages, although they can still make phone calls, F-Secure said.

The Trojan horse also prevents people from installing new applications, so the majority of people with infected handsets will need to reset their phone. This will leave the phone in its default factory condition and delete data such as address books.

F-Secure said it has only had reports of Skulls.D from two people, whose phones were infected after they downloaded an application from a Web forum. Phone owners can reduce the risk of infection by exercising caution, said Mikko Hypponen, the director of antivirus research at F-Secure, which has posted an advisory.

"Be careful about what you download and where you download it from," Hypponen said. "You are most at risk if you are downloading illegal copies of applications, especially from peer-to-peer networks."

Hypponen warned there are likely to be more Skulls in the future. "We are waiting for the next variant," he said.